Stephen Jones to Mike Florio at ProFootball Talk:
[…] when you got a great player like Tony, if you feel like he could infuse some energy and pull something out for you that maybe things aren’t going your way then certainly that’s a coaching decision that can be made by Jason and Scott [Linehan].
Mike then goes on to write:
The possibility of Romo entering a game where “maybe things aren’t going [their] way” raises an alternative to Prescott or Romo being the clear-cut starter. In 2007, the Cardinals used both Matt Leinart and Kurt Warner, typically inserting Warner after the team fell behind and then going back to Leinart once Warner brought the Cardinals back.
This would be an interesting strategy that could allow the Cowboys to play each quarterback to their own strengths. We already have players at other positions who are inserted to fill a certain role or when the situation calls for them.
Either way, I don’t think the Cowboys could go wrong with who they put under center.